The invention relates to a centering circuit for a television deflection system.
Deflection systems utilized in television receivers frequently include circuitry which allows for the adjustment of the centering of the raster on the face of the kinescope tube. The need for this centering feature is increased as overscan of the kinescope tube is reduced, that is, as the raster width approaches the width of the kinescope tube face. Centering is usually accomplished by causing a direct current of selected polarity and amplitude to flow through the deflection coils.
The more efficient prior art arrangements utilize centering circuitry placed in parallel with the deflection windings to produce an average current through the deflection winding during the trace interval. This centering circuitry includes a non-symmetrical conduction network including an adjustable resistor and an integrating inductor in series combination for rectifying some of the scanning current. The nominal resistance of the adjustable resistor and the impedance of the integrating inductor in this arrangement must be relatively large as compared to the impedance of the deflection winding since the same voltage exists across the centering circuit that exists across the deflection winding and only a small fraction of the current through the deflection is conducted through the centering circuit. Hence there is a relatively large amount of power dissipated in the centering circuit.